Rail pads are used to electrically and dynamically insulate the rail tie from the rail and U.S. Pat. Nos. 4,618,093 and 5,203,502 are examples of rail pads used with elastic rail clip support shoulders that are fixed to the tie on either side of the rail.
Often shims and gaskets are also placed under the rail pad.
It is now common practice for the rail pads to be placed in the rail seats at the rail tie manufacturing plant in order to save time at the track installation. The ties are usually stacked on flat rail cars at the tie plant. There may be 4 layers of ties with wooden dunnage between each layer. The dunnage sits on the rail seats. The pads gaskets and shims on the top layer may be blown off in transit or from any tie during installation. If this is not noticed and the rail ties are fed onto the track this can create difficult problems as the rail is automatically fed onto the ties even if the pads are not in place. Then the pads must be inserted after the mobile tie installation machinery has passed. This is difficult expensive and time consuming.
Anther component of the rail fastening system is the insulator that lies between the rail and the rail fastener. U.S. Pat. No. 4,379,521 is an example of such an insulator.
A recent development affecting the design of rail pads has been the adoption of deep post rail insulators where the portion of the insulator lying between the support shoulder and the rail flange extends below the bottom of the rail which means that the rail pad has to be modified to accommodate the deep post insulator. The deep post insulator can be accommodated by making a cut out in the edge of the pad. However this means that this type of pad is not suitable for pre assembly with the shoulders because it needs to be precisely located between the shoulders to accept the insulator post and it is difficult to reposition the pad when the rail is sitting on it. One attempt as shown in U.S. Pat. No. 5,692,677 has been to make the vertical post of the insulator slightly shorter so that a thin section of pad remains to locate the pad against the shoulder. The difficulty of this approach is that the thin section abutting the shoulder is not strong enough to locate the pad against the shoulder.
Another difficulty with insulators of the type disclosed in U.S. Pat. No. 4,379,521 is that they wear out or break before the other components in the rail seat. A problem associated with rail pads has been that under the creep load conditions such as on slopes the rail under the load of trains passing tends to creep relative to the rail seat and under this force the pad may be forced out of position . One approach to dealing with that problem is to provide an upstanding projection on the outer edge of the pad adjacent the insulator so that movement of the pad would be inhibited because movement of the post would be resisted by the insulator. This approach still allows considerable pad movement because of the tolerances required to ensure that the insulators could be fitted.
It is an object of this invention to address the above mentioned problems.